Expansible molding core



'convenient' point .to

Patented Oct 7, 1952 :imamsA kgammes "EXPANsmL-E MoLDINGtooRE Sylvania This invention relates'-toa fornivprimarily-intended foruse in moldingconcrete-bodies.

The production` ofholloW-fconcrete.-bodies Evsu'ch as tunnel linings, pipes,l caissons,=-and"columns, for example, has customarilyrequidtheuse Lof composite internal forms lwhich@must-Hbeidismantledafter-each' castingf-loperationea-nd fthen reassembled for 'the-next Inflatab1e`-1-forms -of known types have notbeenfsuitable-f-or such-purposes, since they would notproduce??theV accuracy `and finish required vfor many structuresof these types.

Inaccordancewith is provided a v unitaryl v'the present invention there expansible' internal for-m tively rigid fcore,1 a; relativelyi'yieldablerresilient tubular metal f shell having a-relativelyfhi-gh 7'yield point surrounding- -the 'core; the 'shellrhav-ing f its ends secured to-'the-core--inf'fluid"tight relationship,` and meansl defining-a `passagei'or introducl ing fluid under'p'ressure betweenff-thef-'coreland shell to expand the-shell. p

` At least one end Iof`-theslfie1lis preferably-hreduced to facilitate-removalofftheirorm fromthe for vrhollow concrete vbodiescerniprisingsafa rela- T5 molded body afte'rfthe 'Llatterehasbecome-self 25 supporting. Y In -a great manylapplicationsgthe of pressure will impose1 forces thereon;ulongitudinally as Well-as radi lly-toincrease itsfexpan'sion andY contraction corresponding to `aq'givenv pressure .30

differential. The'core itself is-pr'eferably-offtubular A metal vconstructionb'andfmaybe intern-ally reinforced byreinforeingsa'nnuli:securedlwithin it inspaced relationship.

The fluid passage mayfpenetratethe coreefatfa-g35 vad-mit'. -rgaseousf or? liquid-material under pressure for expanding #the -shell and/or to permit withdrawal of gaseous or'liquid material from thefcharnber'denedrbetweenthe 'core and shell. 4

For manyl of the -us'escontemplatedlfthe.shell will have i a circular-.crossesection: andf in most such cases, it L-W-illV be'--substantially-cylindrical y throughout a substantial I portion i' lof "-its'-length.

The introduction' ofl'-u'id funden pressure into'- 'the .35.5

chamberbetWeen-the core-and shellwill produce expansion of the relativelyyieldable shellf'the extent of which can` approachdts#elasticlimit. Concrete is poured labout the iorrnfinl-i-tseexpandedcondition, becomes solidiiedl and-self supporting-fthepressure will be removed vanditheshells-willcontract due to its inherent elasticity',r permitting its-ready Withdrawal from-theecast-body. l'Cor-itraction'fof the shell Kcan be increased-"by-fcreating 9.' reduced 2 lpressureWithin the-chamber kthrough the :useof a-vacuumpump.

Armore"complete-understanding: of :the 'invention Wilt follow-from a zdetailedldescription.of tithe accompanying draW-ings'wherein:

Fig. 1 is a sectional elevation of an internal form-v Afor molding tubular-1concretebodies;

fi Fig. 3 is Lan elevation"partially'y in-seetion-depicting a form suitable*fiormoldingrtunneliningsyand y Fig.-- 4 aV sectional '..elevationftaken along" line 4 4 of Fig.3.

1 Wtnparticulan reference to the. iorm depicted --in-Figs- 1 rand' 2 i. a-relativelyv rigidi ltub'ulancore -`l D' which -isfsubstantially cylindricalthroughout the man' or 'I portion lof- -its' ,leng'lth,- has :one @of lits ends f i2l outwardly flared by s--vi-rtue' '.ofl` iitsldiverging-internalhvvall 14 and externali-wa'll 46. Sur- -round-ingthe core ipthere Aisflprovlided .a coaxial and# `coextensive tubularI metal-ifsh'ell i8 having a reduced'convergent endfi2-0-secured to vthe core by a Welded joint 22, and a divergent ilaringaend "24 -fsecured to Y theffiaredend -fofthe-core v.by a Welded jointlZG.

The envelopef--'afdeiined by fthe interconnected =core and "'shell provides: a 4ichambienfawhose internal`A pressure-cana-be-f modied byl introducing for -withdrawing #fini-d. em-passage fon-'such iuidis *defined-'by .means of ai nipple mpenetratingithe `core at a suitable. point;lfoncommunicationswith external -pumps,as`-"through va maniz'foldtfB'Z having branches --34 =andil36 providedfwithstop.-valves 38 and 40 respectively. v

The "-i-nternaliorm 'shoWnoiniF-igs: 1 and' 2;.can be 'utilized in various iways.- 1^P1o1fexample; ,1assuming' ltl'iat'fthe linternal'vi'orm :has4 ibeenwposi- 'tioned-vvith -respecttd.ai-suitable:externaleform, v`-lthe vali/e!` 38e cansbe :opened fomcommun'cati'on 4with Tva vacuum pummrthe .yalvefrd i ibeingf; closed, :whereupon the shell i-ts'ivvillstend .to .conform-zito lthe-fexternal-Wall- I'G'of'f'the core.y Alplastic con- -'crete mixi imaylthenu bendeposited:abouti:thehinwternalforrn and suitablycompaotedbyfyibration,

whereupon i-the vali/ewa' canidoe ,closed a1-nd the Avvra-life Unopened to admita suitable suideisuch .1 as: water, 1 underi pressure ffromuaepunipsthnough fithebranch lpipe1n"6-,f io'pen :valve iimimairriioldz and -`aszsoon'as the lplaStic-'mass :350 Aand nipple3.0,:` into thelzenvelope denedszbyigthe interconnected ooreiarid shell; l'lgexshellizBL-.Wiil thenzbe. 1extended.,.iradially with '.-irespect stof its :relatively rigid'.` core L0 toucomp'act the; conc-rete .lto'ua greater: extent. t Themtclafteiuitlie;camerate `tunnel lining.

closed, the valve 38 opened to again contract the shell, and the form as an entirety can be withdrawn from the molded product with facility.

It is contemplated that the resilient metal shell I8 have a minimum yield point of fifty thousand 5 pounds per square inch and a stiffness far in excess of that obtainable with rubber bags of the types that have.' beenV proposed for inflatable forms in thepast. Assuming that the internal cylindrical diameter of the shell is thirty-six inches and the maximum internal diameter of the ared portion is forty-eight inches, and fur ther assuming that a subatmospheric pressure of twenty-five inches of mercury is provided' through the nipple 30, the pull tending to flatten the shell will approximate five tons. rlhis will follow from the relationship:

De.. 2) 4 2o where P is thepull in pounds, D is the maximum diameter of the iiared portion, d is the diameter of the cylindrical portion, and the value 12.5 is the pressure in pounds per square inch corresponding to a vacuum of twenty-five inches of mercury. f y

In a similarmanner, for a tunnel having a diameter of twenty feet, where the diameter of the flared portion of the shell has amaximum measurement oftwenty-one feet, the pull will be computed as approximately 29.5 tons.

Another manner in which the form can be employed is by introducing fluid underV pressure through the branch pipe 36 and valve et, the valve 38 being closed, prior to pouring the con-V crete, therebyextending the shell to a desired degree, then pouring .the concrete, and after the material hasbecome suiiiciently hardened and self-supporting, the valve ll can be closed, the valve `38 opened, and the effect of subatmospheric pressure utilized to contract the shell from its contact with the molded material, whereupon the form ,as an entirety can be removed as a unit. 1, Y

Somewhat similar apparatus has been depicted in Figs. 3 and 4 as applied to the forming of a An external form 42 may be defined by -a suitable excavation, the left end of the internal ,formbeing supported upon previously formed and hardened concrete ed. The right end of the form will be supported in a suitable manner, substantially centered within the outer form 42, whereupon concrete in a plastic condition can be poured between the internal and external forms.

In this case, the shell I8 has been depicted as reduced at both ends and welded to the ends of the core l0. Here again, the shell is composedv of resilient metal, preferably having a yield point in excess of fifty thousand poundsI per square inch, yet relatively yieldable as compared with its core l0. The wall thickness, and accordingly the weight, of the core I 0 can beV somewhat reduced by using internal reinforcements inthe form of spaced annuli 46 welded to ther internal,n wall I4 of the core at suitable intervals. VI-lere again, the core ispenetrated by a nipple VV3i) which is connected through a manifold 32 with a branch pipe 34 leading to a vacuum pump and provided with a valve 38, and a ,branch` pipe` 36 leading to a pressure pump and provided with a-valve 4U.

The operation of th-e apparatus depicted in Figs. 3 and 4 may be similar to that described with reference to Figs. 1 and 2. In other Words, the shell may be contracted before the concrete is poured, then expanded to compact' the con-- l`for movement to its new position.

Whereas only two forms of the invention have been illustrated, variations will occur to those skilled in the art, just as they have been recognized already by the present inventor. Accord- `ingly, the invention should not be restricted to the examples shown beyond the appended claims.

I claim:

scope of the l. An expansible internal form for hollow con-1 crete bodies comprising a relatively rigid core,

a relatively yieldable resilient tubular metal shell surrounding said core, said shell having two longitudinally` spaced kends secured to said core in fluid tight relationship defining a chamber, said.

shell having a divergent portion adapted for ex posure to atmospheric pressure adjacent one off said ends, and means deningl a passage com-v municating with said chamber for modifying the fluid pressure between said core and shell to dis-- place'portions of said shell radially and longi tudinally relative to said core.

2.a-An expansible internal form for hollow con crete bodies comprising a relatively rigidcore,

a relatively yieldable resilient tubular metal shell surrounding said core,` said shell having two longitudinally spaced ends secured to said core in fluid tight relationship defining a chamber, atk ,least one of said ends being reduced, at least one of said ends being adapted for exposure to atmospheric pressure externally thereof, and means defining la passage communicating. with said chamber for modifying the iiuid pressure between saidvcore and shell to extend a portion of said shell longitudinally relative to said core as a function of the diferentialbetween said fluid pressure and atmospheric pressure.

3. An expansible internal form for hollow concrete bodies comprising a relatively rigid tubular core, a relatively yieldable resilient tubular metal shell surrounding said core, said shell having two longitudinally spaced ends secured to said core in fluid tight relationship defining a chamber, 'said shell andcore` flaring towards One of said ends, at least one of said ends being adapted for exposure to atmospheric pressure externally thereof during a molding operation, and means defining a passageV communicating with said chamber for introducing fluid under pressure between said coreand shell to expand said shell krelative to saidA core.

4.',An expansible internal form for hollow concrete bodies comprising a relatively rigid tubular :members secured within said core, and means defining. a.A passage communicating with said chamber for introducing huid under pressure between ysaid core and shell into contact with one ,ofvsaid surfaces to expand said shell.

.5. An expansible internal form for hollow concrete-bodies .comprising a relatively rigid core, a relatively yieldable resilient tubular metal shell surrounding said core, said shell having two 1ongitudinally spaced ends secured to said core in fluid tight relationship denng a chamber, said shell having a divergent Wall radjacent one of said ends for exposure to unequal fluid pressures 5 on opposite surfaces thereof, spaced reinforcing annuli secured within saidcore, and means dening a passage communicating with said charnber for introducing fluid under pressure between said core and shell into contact With one of said 10 surfaces to expand said shell.

' KARL P. BILLNER.

REFERENCES CITED The following references are of record in the 15 le of this patent:

Number Numb er 6 UNITED STATES PATENTS Name Date Maddook et al. Feb; 17, 1903 Mauersberger Aug. 10, 1915 Freyssinet et al. 'Sept 1, 1936 Price Dec. 29, 1941 Terry Nov. 21, 1945 Fitzpatrick Feb. 19, 1946 FOREIGN PATENTS Country Date France 1 Jan. 29, 1919 

